1. Field of the Invention
The present invention relates to a glycoprotein facilitating species-specific bonding of sperm to zonae pellucidae, and a process for production of the glycoprotein.
2. Description of the Related Art
For fertilization in mammals, sperm must reach the zonae pellucidae forming the outer membrane of the ovum. The zonae pellucidae is considered to play an important role, such as inter-species recognition and the rejection of polyspermy to establish monospermy, etc., during fertilization. However, substances involved in such processes are still not entirely clarified. The present inventors developed a method for the preparation of a large amount of mammalian ovum by an experimental system using pig ovaries, Gamete Res. 1, 265-267 (1978). This method was then modified by Dunber, B. S. et al., Biochemistry, 2, 356-365 (1980), and Gwatkin, R. B. L. et al, Gamete Res., 3, 217-231, (1980). Using this modification, Dunber, B. S. et al, Biol. Reprod., 24, 1111-1124 (1981) found that the zonae pellucidae of an immature ovum from pigs and rabbits contains three kinds of glycoprotein, designated as ZP-1, ZP-2, and ZP-3, respectively. However, the composition of the substances in the zonae pellucidae of a matured ovum, which directly receive the sperm, has not been clarified.